自定义select组件onchange/onfocus事件无法触发问题求助

问题描述 #

参照自定义select示例实现组件后，无法触发原<select>的onchange和onfocus事件，自定义选项也无法执行预期事件，需要为组件正确绑定事件。

解决方案 #

1. 手动触发原Select的change事件 #

原<select>被设置为display:none，无法通过原生交互触发change事件，需要在自定义选项的点击回调中，更新原select的选中状态后手动触发该事件：

c.addEventListener("click", function(e) {
  var y, i, k, s, h, sl, yl;
  s = this.parentNode.parentNode.getElementsByTagName("select")[0];
  sl = s.length;
  h = this.parentNode.previousSibling;
  for (i = 0; i < sl; i++) {
    if (s.options[i].innerHTML == this.innerHTML) {
      s.selectedIndex = i;
      // 新增：触发原select的change事件
      s.dispatchEvent(new Event('change'));
      h.innerHTML = this.innerHTML;
      y = this.parentNode.getElementsByClassName("same-as-selected");
      yl = y.length;
      for (k = 0; k < yl; k++) {
        y[k].removeAttribute("class");
      }
      this.setAttribute("class", "same-as-selected");
      break;
    }
  }
  h.click();
});

2. 绑定focus与blur事件 #

给自定义的.select-selected元素添加tabindex使其可聚焦，再同步绑定focus和blur事件到原select：

// 在创建.select-selected元素后添加：
a.setAttribute("tabindex", "0"); // 让div获得焦点能力
a.addEventListener("focus", function() {
  var s = this.parentNode.getElementsByTagName("select")[0];
  s.dispatchEvent(new Event('focus'));
  // 聚焦时自动打开下拉框
  closeAllSelect(this);
  this.nextSibling.classList.remove("select-hide");
  this.classList.add("select-arrow-active");
});

a.addEventListener("blur", function() {
  // 延迟关闭，避免点击选项时直接触发blur导致下拉框提前关闭
  setTimeout(() => {
    closeAllSelect(this);
    this.nextSibling.classList.add("select-hide");
    this.classList.remove("select-arrow-active");
  }, 150);
});

3. 修复closeAllSelect函数逻辑bug #

原函数中判断条件错误，会导致下拉框无法正确关闭，修正如下：

function closeAllSelect(elmnt) {
  var x, y, i, xl, yl, arrNo = [];
  x = document.getElementsByClassName("select-items");
  y = document.getElementsByClassName("select-selected");
  xl = x.length;
  yl = y.length;
  for (i = 0; i < yl; i++) {
    if (elmnt == y[i]) {
      arrNo.push(i);
    } else {
      y[i].classList.remove("select-arrow-active");
    }
  }
  for (i = 0; i < xl; i++) {
    // 修正：只有当索引不在arrNo中时才隐藏
    if (arrNo.indexOf(i) === -1) {
      x[i].classList.add("select-hide");
    }
  }
}

4. 正确绑定原Select的事件监听 #

确保在DOM加载完成后绑定原select的事件，避免元素未初始化导致绑定失败：

document.addEventListener('DOMContentLoaded', function() {
  let selectDiv = document.getElementById('selectopt');
  selectDiv.addEventListener('change', function() {
    console.log('选中值变更:', this.value);
  });
  selectDiv.addEventListener('focus', function() {
    console.log('select获得焦点');
  });
});

修改后的完整JavaScript代码 #

var x, i, j, l, ll, selElmnt, a, b, c;
x = document.getElementsByClassName("custom-select");
l = x.length;
for (i = 0; i < l; i++) {
  selElmnt = x[i].getElementsByTagName("select")[0];
  ll = selElmnt.length;
  a = document.createElement("DIV");
  a.setAttribute("class", "select-selected");
  a.setAttribute("tabindex", "0"); // 添加焦点能力
  a.innerHTML = selElmnt.options[selElmnt.selectedIndex].innerHTML;
  
  // 绑定focus事件
  a.addEventListener("focus", function() {
    var s = this.parentNode.getElementsByTagName("select")[0];
    s.dispatchEvent(new Event('focus'));
    closeAllSelect(this);
    this.nextSibling.classList.remove("select-hide");
    this.classList.add("select-arrow-active");
  });
  
  // 绑定blur事件
  a.addEventListener("blur", function() {
    setTimeout(() => {
      closeAllSelect(this);
      this.nextSibling.classList.add("select-hide");
      this.classList.remove("select-arrow-active");
    }, 150);
  });
  
  x[i].appendChild(a);
  
  b = document.createElement("DIV");
  b.setAttribute("class", "select-items select-hide");
  for (j = 1; j < ll; j++) {
    c = document.createElement("DIV");
    c.innerHTML = selElmnt.options[j].innerHTML;
    c.addEventListener("click", function(e) {
      var y, i, k, s, h, sl, yl;
      s = this.parentNode.parentNode.getElementsByTagName("select")[0];
      sl = s.length;
      h = this.parentNode.previousSibling;
      for (i = 0; i < sl; i++) {
        if (s.options[i].innerHTML == this.innerHTML) {
          s.selectedIndex = i;
          s.dispatchEvent(new Event('change')); // 触发change事件
          h.innerHTML = this.innerHTML;
          y = this.parentNode.getElementsByClassName("same-as-selected");
          yl = y.length;
          for (k = 0; k < yl; k++) {
            y[k].removeAttribute("class");
          }
          this.setAttribute("class", "same-as-selected");
          break;
        }
      }
      h.click();
    });
    b.appendChild(c);
  }
  x[i].appendChild(b);
  
  a.addEventListener("click", function(e) {
    e.stopPropagation();
    closeAllSelect(this);
    this.nextSibling.classList.toggle("select-hide");
    this.classList.toggle("select-arrow-active");
  });
}

function closeAllSelect(elmnt) {
  var x, y, i, xl, yl, arrNo = [];
  x = document.getElementsByClassName("select-items");
  y = document.getElementsByClassName("select-selected");
  xl = x.length;
  yl = y.length;
  for (i = 0; i < yl; i++) {
    if (elmnt == y[i]) {
      arrNo.push(i);
    } else {
      y[i].classList.remove("select-arrow-active");
    }
  }
  for (i = 0; i < xl; i++) {
    if (arrNo.indexOf(i) === -1) {
      x[i].classList.add("select-hide");
    }
  }
}

// 点击页面其他区域关闭下拉框
document.addEventListener("click", function() {
  closeAllSelect();
});

// 绑定原select的事件
document.addEventListener('DOMContentLoaded', function() {
  let selectDiv = document.getElementById('selectopt');
  selectDiv.addEventListener('change', function() {
    console.log('选中值变更:', this.value);
  });
  selectDiv.addEventListener('focus', function() {
    console.log('select获得焦点');
  });
});

内容的提问来源于stack exchange，提问作者KrupaV